If you are asked that question this is the sort of answer you give:

"I was given an opportunity to lead a product I was very excited about, and I took it. It was a great experience, and I learned a lot, but ultimately now I'm glad to be moving back into a developer role."

If you can truthfully say that, you're conveying not indecision, but rather showing the flow of your career path. That is something that is expected to take a few twists like this, and that's even a sign that you're someone with flexibility and a variety of skills, as opposed to being inflexible and unwilling to do things that are "outside the box".

And if you have leadership experience, you could always step back into that role if the needs of the company change (e.g. project lead leaves the company and they need someone to fill in until they get a replacement).

My previous company saw project management as a step up, whereas I see it as just another role. Many engineers make poor project leads, and many project leads make poor engineers. Unfortunately, our society values "people" jobs like leadership positions more than technical jobs, so people will see it as a downgrade (especially those in management).

Ignore that noise and do the thing you like that helps you meet your other goals (financial, lifestyle, etc).

I've been on both sides, and I interview a lot of engineers now as a product person. If I heard this from an interviewee, especially given your context in this thread, I would not view it as indecisive. To the contrary, I would credit the interviewee as ambitious and a lifelong learner.

If it were me hiring I would probably see this as a positive thing - not only are you an experienced developer but now you also have some experience of doing product management as well. That gives you a different perspective to most developers, and means that you'll likely be better at working with the product team to define what you can/should be doing.

If you switch and then quickly switch back because you realised that it was a mistake - that's no big deal.

If you switch roles and after a couple of years switch back again - no problem!

If you start to have a history of every six months to a year switching roles or moving companies, that can start to look bad, yes. But even that isn't a disaster that can't be overcome.

I wouldn't worry about it.

Developers trying a management role and then returning to development is relatively common. You shouldn't worry if you wish to try it out for a year or two.

Yes, when hiring developers I see that as a positive: often people with this kind of background can tackle larger projects well due to good self-organization.

As a bonus, they tend to have more empathy for what i have to deal with, so when they ask for support or process changes their ideas tend to be practical and reasonable.